Load switch with parallel connected capacitors



June 29, 1965 P. BALTENSPERGER 3,

LOAD SWITCH WITH PARALLEL CONNECTED CAPACITORS Filed Sept. 7, 1961 2 Sheets-Sheet 1 Paul fialfens gzi g fi Jamil Jvzl agwz PM LOAD SWITCH WITH PARALLEL CONNECTED CAPACITORS Filed Sept. 7, 1961 June 29, 1965 P. BALTENSPERGER 2 sneets-sht 2- Fig.9

150w 220w 300KV 4-OO-KV lO-M INVENTOR- PauL Boliensperger United States Patent 0 3,192,440 LOAD SWITCH WITH PARALLEL CONNECTED CAPACITORS Paul Baltensperger, Wurenlos, Aargau, Switzerland, as-

signor to Aktiengesellschaft Brown, Boveri & Cie, Baden, Switzerland, a joint-stock company Filed Sept. 7, 1961, Ser. No. 136,502 Claims priority, application Switzerland, Sept. 16, 1960, 10,495/ 60 6 Claims. (Cl. 317-11) This invention relates to electrical switches for switching heavy load currents of the alternating type and more particularly to switches of this type provided with a plurality of load breaking points connected electrically in series and wherein impedances are connected in parallel with, i.e. shunted across, the load breaking points. The function served by these impedances, in the known constructions, is to distribute in a uniform manner the potential of the recovery voltage on the breaking points. Moreover, the impedances serve to damp or level off the frequency of the recovery voltage, particularly in cases where this voltage has a steep rise.

No capacitances or high ohmic resistance-s are needed for the equalization of the potential. On the other hand, low ohmic resistances or great capacitances must be used for the eifective smoothing of the rise in recovery volt age. In order to meet both requirements, low ohmic resistors have hitherto been shunted additionally with the potential distribution capacitances. The damping of the recovery voltage can now also be obtained with the help of capacitances if these have an adequately great can ;have the same eifect, and additional favorable characteristics are added thereto. The function performed by a capacitance connected in parallel with the switch gap is to furnish a discharge current into the path of the are at a time just before the current passage through zero, approximately between the extinguishing peak of the arc voltage and the attainment of zero of the latter, this discharge cu-rrent being superimposed upon the inductive, short-circuit current furnished by the feeding network to which the switch is connected, whereby the resulting switching current approaches Zero just before its actual passage through zero, with less steepness as regards time than what would be the case were no paralleling capacitance to be present. The slower current zero passage facilitates the electric arc extinction by the switch. Even during the rising recovery voltage, the capacitance takes over the current like a low-ohmic resistance and thus it relieves the switch path simultaneously with the smoothing of the recovery voltage. For these reasons, such capacitances are additionally shunted with the entire switch, which, however, causes a disadvantage to the effect that more impedances must be provided additionally for the potential control impedances.

Furthermore, it has been made known that the parallel capacitances for the potential control can be arranged in various sizes to be able to balance the various selfcapacitances of the individual breaking points.

In order to save the above mentioned extra expenditure it is now suggested, in accordance with the invention, for load switches with shunt capacitances and multi- 3,192,449 Patented June 29, 1965 "ice ple breaking points where the capacitances shunted with the individual breaking points, have different values, that, at least, one breaking point should have a shunt capacitance which, independent of the potential distribution on the individual breaking points, is at least equal to the triple value of the capacitances of the remaining breaking points.

Hereby the potential control becomes, indeed, impaired to a minimum extent, however, a simpler and cheaper construction is obtained inasmuch as the capacitor used for the smoothing of the rise in the recovery voltage, can be designed for a lower voltage than in the known constructions.

If resistors are used for the potential control, it is also feasible, to design one of these resistors in such a way that it has maximally one third of the resistance at the remaining breaking points. It is even feasible to go so far that the shunt capacitances are provided only at just one breaking point if the self-capacitance for the potential control sufiices for the remaining breaking points.

The advantages of the invention will become more apparent from the following detailed description of several embodiments thereof and from the accompanying drawings wherein: V

FIG. 1 is a circuit diagram showing one embodiment wherein the load switch comprises two breaking points connected electrically in series and wherein capacitors are shunted across each breaking point;

FIG. 2 is also a circuit diagram showing a switch with two series arranged breaking points and wherein a capacitor is shunted across only one breaking point;

FIG. 3 is a circuit diagram of an embodiment similar to that of FIG. 1 and wherein resistors are also shunted across each of the two breaking points of the switch;

FIG. 4 is a circuit diagram of a further embodiment similar to that of FIG. 1 and wherein one resistor is shunted across the series connection of the two breaking points;

FIG. 5 is a circuit diagram of a further embodiment wherein several breaking points of the load switch are each shunted by a capacitor and a resistor;

, FIG. 6 is a circuit diagram of another embodiment wherein the load switch is provided with two groups of series arranged breaking points, wherein the breaking points of each group are each shunted by a capacitor and wherein a resistor is shunted across each group of the series arranged breaking points;

FIG. 7 is a circuit diagram of a further embodiment wherein the load switch is provided with two groups of series arranged breaking points and wherein the breaking points of each group are shunted by a single capacitor and by a single resistor;

FIG. 8 is a circuit'diagram of another embodiment wherein the load switch has two series arranged breaking points, one of these breaking points being shunted by a capacitor and the other shunted by an inductor; and

FIG. 9 illustrates the invention wherein a capacitor is shunted across one of several breaking points for several load switches designed for different operating voltages.

With reference now to FIG. 1 it will be seen that the load switch is comprised of two breaking points 1, 2 arranged electrically in series. Each breaking point is characterized by the customary pair of relatively movable contacts. A capacitor 3' having a great capacitance is shunted across breaking point 1 and another capacitor 4 having a smaller capacitance is shunted across breaking point 2.. In the embodiment of FIG. 2 which is similar to that of FIG. 1, only the breaking point 1 is shunted by a capacitor 3 having a large capacitance while the other breaking point 2 has only its self-capacitance.

FIG. 3 shows another embodiment comprising load breaking points 1, 2 arranged in series, there being a large capacitor 3 shunted across breaking point 1 and another smaller capacitor 4 shunted across breaking point 2. In addition, a resistor 5 having a low ohmic value is connected parallel with breaking point 1 and capacitor 3, and a resistor 6 having a high ohmic value is connected parallel with breaking point 2 and capacitor 4. Resistor 6 must have an ohmic value at least three times greater than that of resistor 5.

In the embodiment of FIG. 4, the breaking point 1 is paralleled by a large capacitor 3 and breaking point 2 is paralleled by a smaller capacitor 4. In addition, a single resistor 5 is connected in parallel across the two series arranged breaking points.

FIG. 5 illustrates an embodiment of the invention wherein the load switch is comprised of two groups of load breaking points arranged in series, one group of the breaking points being designated 1.1, 1.2, 1.3 1.11

while the other group is designated 2.2, 2.3 2.111. Capacitors 3.1, 3.2, 3.3 and 3.11 are shunted with their respective breaking points 1.1 to 1.1: and capacitors 4.1, 4.2, 4.111 are shunted with their respective breaking points 2.2 to 2.111. The capacitors 3.1 to 3.11 have at least triple the capacitance of capacitors 4.1 to 4111. Resistors 5.1, 5.2, 5.3 and 5.72 are shunted with their respective breaking points 1.1 to 1.11 and resistors 6.1, 6.2 and 6.111 are shunted with their respective breaking points 2.2 to 2.111. The resistors 5.1 to 5.11 have a lower ohmic value than the resistors 6.1 to 6.111. In the embodiment of FIG. 5, the letters m and 11 signify the number of breaking points of the switch, m and 12 can be equal or different.

The embodiment illustrated in FIG. 6 is quite similar to that illustrated in FIG. 5 except that a single resistor 5 is shunted with all of the breaking points 1.1 to 1.11, and another single resistor 6 is shunted with all the breaking points 2.1 to 2.111. As in FIG. 5, resistor 5 has a lower ohmic value than resistor 6.

The embodiment of FIG. 7 is also similar to FIG. 5 except that a single capacitor 3 is shunted with all of the breaking points 1.1 to 1.11 and a single capacitor 4 is shunted with all of the breaking points 2.1 to 2.m.

In the embodiment of FIG. 8, it will be seen that the switch also comprises two load breaking points 1 and 2 arranged in series and wherein a capacitor 3 is shunted with breaking point 1 while an inductor 7 is shunted with breaking point 2.

The advantage of the various embodiments which have been described resides in the fact that a breaking point with a great capacitance shunted with the same can break the current (due to the gradually rising transitory recovery voltage through this breaking point) in connection with transitory recovery voltages with a high, upper frequency of small amplitude as they occur in the spacing short circuit, while the breaking points arranged in series disconnect their current somewhat later (e.g. 1 ms.) as the current, which is taken immediately before, during, and after passage through zero from the great parallel connected capacitors at their respective switching points, continues to flow through said parallel capacitors but is limited by them more and more and thus extinguishes in the course of the dying out of the transistory recurrent voltage. Then the great capacitance is loaded with voltage for a short period of time and this voltage becomes reduced and amounts to only a fraction of the operating frequency pole voltage.

The production costs of the capacitor with great capacitance are thus reduced. Even at high operating voltages, it is thus feasible toselect a smaller strength of insulation. Then the same capacitors can be applied even for several switch types operating at various voltages. This is illustrated diagrammatically in FIG. 9 wherein it will be observed that several load switches designed for various operating voltages from kv. to 400 kv. are represented. The same capacitor 3 is always applied to these various switches. Besides the simplification of production and reduction in number there is also achieved a simplification in storekeeping for the capacitors.

I claim:

1. In a load switch including a plurality of breaking points arranged electrically in series, each such breaking point being established by the gap between two relatively movable switching contacts, and wherein each such breaking point includes a capacitance in shunt therewith, the improvement wherein at least one breaking point is provided with a capacitor in shunt therewith, the capacitance value of said capacitor indepedently of the potential distribution through the individual breaking points being at least triple the value of the capacitances of the remaining breaking points.

2. A load switch as defined in claim 1 wherein ohmic resistors are connected in parallel with said capacitors and the resistor disposed in parallel with the capacitor of great capacitance value has at most one-third of the resistance value as compared with the resistance connected in parallel with the small capacitances.

3. A load switch as defined in claim 1 wherein said capacitor with great capacitance value is provided for one breaking point only, the remaining breaking points having their self-capacitance only.

4. A load switch as defined in claim 2 wherein only one resistor is provided, said resistor being connected in parallel to the series connection of all breaking points on the switch.

5. A load switch as defined in claim 2 wherein the resistors and capacitors of several breaking points are References Cited by the Examiner FOREIGN PATENTS 4/50 Great Britain. 8/58 Great Britain.

SAMUEL BERNSTEIN, Primary Examiner. 

1. IN A LOAD SWITCH INCLUDING A PLURALITY OF BREAKING POINTS ARRANGED ELECTRICALLY IN SERIES, EACH SUCH BREAKING POINT BEING ESTABLISHED BY THE GAP BETWEEN TWO RELATIVELY MOVABLE SWITCHING CONTACTS, AND WHEREIN EACH SUCH BREAKING POINT INCLUDES A CAPACITANCE IN SHUNT THEREWITH, THE IMPROVEMENT WHEREIN AT LEAST ONE BREAKING POINT IS PROVIDED WITH A CAPACITOR IN SHUNT THEREWITH, THE CAPACITANCE VALUE OF SAID CAPACITOR INDEPENDENTLY OF THE POTENTIAL DISTRIBUTION THROUGH THE INDIVIDUAL BREAKING POINTS BEING AT LEAST TRIPLE THE VALUE OF THE CAPACITANCES OF THE REMAINING BREAKING POINTS. 